1. Field of the Invention
This invention relates to a method of imparting a predetermined tension to a tape-like member transported at a predetermined velocity as in tape recorders.
2. Description of the Prior Art
Heretofore, in a tape recorder, the tape transported by a capstan has been taken up from one reel onto another in such a manner that a rotational torque is imparted to the reel spindle on the take-up side to prevent occurrence of slack in the tape while a tension is imparted to the tape to cause the tape to frictionally engage a head with a suitable contact pressure and a brake torque is imparted to the reel spindle on the supply side to stabilize the transport of the tape.
Usually, however, the rotational torque and brake torque so imparted to the take-up reel spindle and the supply reel spindle are constant but the tension imparted to the tape is greatly variable by the amount of the tape wound on the reel mounted on each of the reel spindles. Let the tape tension be T.sub.e, the torque of the reel spindle be T.sub.t and the radius of the coiled tape on the reel be r. These are in the following relation: EQU T.sub.e = T.sub.t /r (1)
For this reason, there has been proposed a method of directly detecting the tension in the tape and controlling to impart to the reel spindle such a torque that the tension in the tape becomes constant. However, such method is disadvantageous in that high mechanical accuracy is required and that in the case where the tape is contained in a cassette for example, difficulties are experienced in designing since the space available to detect the tension is limited.